In many RF Systems, such as portable wireless devices, more than one receive frequency or transmit frequency may be simultaneously active in a single radio device. When the respective frequency bands are far away from each other and/or when the frequency bands are processed with different gains, different frequency channels are separated in the frequency domain and processed in separate signal paths. Many systems today require flexible frequency planning and simultaneous processing of more than two channels, which makes a fixed frequency de-multiplexer filter design (with n frequency bands) challenging to design. For example, 4th generation mobile communication standard LTE uses carrier aggregation techniques that utilize multiple channels in which up to three receive (RX) channels and one transmit (TX) channel are processed at the same time. In the next generation LTE standard and likely other standards too, multiple RX paths of different frequencies and multiple TX paths of different frequencies will be operated simultaneously. Accordingly, assuming the TX is filtered out already, the User Equipment (UE) separates up to three RX channels that are split in the frequency domain.